Summary: The Effect of Milankovitch Variations in Insolation on Equatorial Seasonality
YOSEF ASHKENAZY
Department of Solar Energy and Environmental Physics, The Jacob Blaustein Institutes for Desert Research,
Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel
IAN EISENMAN
Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California,
and Department of Atmospheric Sciences, University of Washington, Seattle, Washington
HEZI GILDOR
The Fredy and Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel
ELI TZIPERMAN
Department of Earth and Planetary Sciences, and School of Engineering and Applied Sciences,
Harvard University, Cambridge, Massachusetts
(Manuscript received 1 March 2010, in final form 26 July 2010)
ABSTRACT
Although the sun crosses the equator 2 times per year at the equinoxes, at times in the past the equatorial
insolation has had only one maximum and one minimum throughout the seasonal cycle because of Milan-
kovitch orbital variations. Here a state-of-the-art coupled atmosphere­ocean general circulation model is
used to study the effect of such insolation forcing on equatorial surface properties, including air and sea
temperature, salinity, winds, and currents. It is shown that the equatorial seasonality is altered according to
the insolation with, for example, either maximum sea surface temperature (SST) close to the vernal equinox